I've got a project I want to work on, which involves an LCD, MAX232, and MSP430. The LCD requires 5V for logic and 3V for the backlight. The MAX232 will work from 3VDC to 5.5VDC. The MSP430G2231 will handle 1.8VDC to 3.6VDC.
The main power source is going to be the 12V accessory power circuit in a car. It seems logical to regulate the ~12VDC to 5VDC, and then use the regulated 5V to create the 3.3V needed for the MSP430. I was thinking about trying 3.3V on the backlight -- the specs state 3V typical, but don't specify a min or max value. I plan to see if I can just measure Vf of the backlight and add a current-limiting resistor to the circuit so I can safely use the 3.3V.
Anyhow, since I need two voltage regulators, does anyone have any recommendations for an ideal configuration? It looks like the LCD uses a max of 1.5mA @ 5V, and the backlight takes a max of 45mA. The MAX232 clone uses a max of 1mA @ 3.3V with no load (I have no idea what it would be under load), and the MSP430 looks like it uses about 4.2mA @ 3.3V and 16MHz. I think these are worst-case conditions.
Would you use a switching regulator to go from 12V to 5V, and then a linear regulator to go from 5V to 3.3V? Or one of the really low-count options as in the 3V Tips 'n Tricks from Microchip like a single zener or multiple diodes? I picked up some MC34063s to play with, but am open to anything else with a lower / smaller part count.
LCD specs I used:
I would sure appreciate any comments, like recommended approaches, or if I have flaws in my interpretation of the specs.